It is well understood that heat can be transmitted from one place to another by three mechanisms, namely radiation, conduction and convection.
The benefits of insulating buildings and other structures have long been understood. Typically, buildings and other structures are insulated using poor thermal conductive materials such as fibreglass and wool. These materials are typically used in the walls and ceilings of structures to retard the transfer of heat into the structure during warmer months, and to retard the transfer of heat out of the structure during cooler months.
A number of attempts have been made to develop paints that effectively retard the transfer of heat through a surface to which the paint has been applied. For example, materials such as sodium bicarbonate and steric acid, potassium titanate fibres, glass frit, aluminium flakes, vermiculite, perlite and glass wool have all been considered as possible additives to paint to produce thermally insulating paints. Each of these additives has been of only limited value in producing thermally insulating paints. Further, the inclusion of such additives in paint often detracts from the desirable properties of paint, such as its ease of application to surfaces, and the aesthetic appearance of the paint coating.
One paint product which has been described as having good thermal insulative properties is described in the specification for Australian patent no. 601148. That specification describes a high build paint coating formed from a composition comprising a hardenable liquid paint base, silica particles and bagasse particles, wherein the silica and bagasse particles comprise up to 60 percent by weight of the mixture. This coating is described as being effective in maintaining a reduced temperature in the interior of a structure subject to radiant heat compared to an equivalent unpainted structure. The described composition does however suffer from a number of disadvantages. The described dimensions of the bagasse particles included in the composition make the composition difficult to apply to a surface and may have undesirable effects on the appearance of the paint coating. Further, the large particle sizes of the silica and bagasse particles used in some embodiments of the invention result in coatings which are likely to suffer from fungal problems. The large particle sizes result in a very thin layer of the other components of the composition over the silica and bagasse particles in the coating formed from the composition. In some embodiments, this thin layer does not provide adequate protection from moisture reaching the bagasse particles thereby allowing the growth of fungi. Further, the required thickness of the paint coating to render it effective make the composition an unsuitable product for use in applications where thinner coatings of paint are required, such as interior and exterior house paints and automotive finishes.
The specification for Australian patent application no. 10487/92 describes the use of microcrystalline cellulose particles having an average particle size of 1 to 10 μm in paper coating compositions. The paper coating compositions described in that specification comprise the particles of cellulose in an aqueous suspension. The paper coating compositions described in that specification are said to be useful for enhancing the performance of commercial optical brighteners. There is no suggestion or indication in that document that coatings formed from the compositions disclosed in that document may have an effect in altering the transfer of heat through paper or any other surface to which the coating composition is applied.